MBMS is a point-to-multipoint service carrying capacity introduced by 3GPP in Release 6. Through network resource sharing, including core network and access network resource sharing, air interface resource sharing in particular, MBMS achieves transmission of point-to-multipoint service in which data is transmitted from a single data source to multiple users, so as to enhance the utilization rate of network bandwidth, especially that of air interface resources. MBMS defined by 3GPP can achieve not only multicast and broadcast of the message type in text and at a low rate but also multicast and broadcast of multimedia services at a high rate. Undoubtedly, this conforms to the trend of the development of mobile data in future.
FIG. 1 is an architectural schematic view of WCDMA communication systems providing MBMS. As shown in FIG. 1, the WCDMA MBMS network architecture realizes sharing of air interface resources based on a WCDMA/GPRS packet network and through incorporating into core network 1 new function entities, e.g. broadcast multicast service center (BM-SC) 105, adding the MBMS function to existing packet domain function entities, such as UE 101, a radio network controller (RNC not shown) located inside radio access network (RAN) 102, serving GPRS support node (SGSN) 103 and gateway GPRS support node (GGSN) 104, and defining new logic shared channels. The BM-SC 105, which is connected with multicast broadcast source 106 in public data network 2, is used for authorizing and initiating MBMS services in a mobile network and controlling the transfer of MBMS contents; the SGSN 103 and the GGSN 104, which are located in the core network 1, form a transmission network within the core network in MBMS systems to provide routing for the transfer of packet data, in which the SGSN 103 performs network control for users and the GGSN 104 establishes or releases user interface carrying for the transfer of MBMS service data; and the RAN 102 provides radio resources for MBMS services via an air interface and is responsible for the valid distribution of MBMS service data to service areas of MBMS services.
To support such a new capacity introduced into 3GPP Release 6, there is a need to define in the WCDMA network a series of MBMS service procedures, which are as follows:
MBMS Multicast Service Activation Procedure;
MBMS Session Start Procedure;
MBMS Registration Procedure;
MBMS Session Stop Procedure;
MBMS De-Registration Procedure;
MBMS Multicast Service Deactivation Procedure;
MBMS Broadcast Service Activation;
MBMS Broadcast Service De-Activation Procedure;
MBMS Broadcast Session Start Procedure.
Among them, the MBMS Multicast Service Deactivation Procedure defines signaling interaction and operation to be implemented between the UE 101 and a network when the user equipment UE 101 wishes to cancel a certain activated multicast service. Usually initiated by the UE 101, this procedure aims to remind the network that the UE 101 does not desire data service of the certain MBMS service. Through this deactivation procedure, UE context corresponding to the MBMS service (hereinafter referred to as MBMS UE context) stored in both the UE 101 and the network is deleted. The context is directly related to accurate distribution and transmission of MBMS data.
FIG. 2 is a schematic view of the prior MBMS Multicast Service Deactivation procedure. For the detailed description of the prior MBMS Multicast Service Deactivation procedure, please see 3GPP protocol (TS 23.246 V6.3.0 2004-06). The procedure illustrated in FIG. 2 takes into consideration only the removal of MBMS UE context in the UE 101, the SGSN 103 and the GGSN 104 and does not consider the removal of MBMS UE context stored in the RNC. After the MBMS Multicast Service Deactivation procedure, information on the multicast service which the UE 101 wishes to cancel is no longer on either the UE side or the core network side. That is to say, after the procedure, there will be no other trigger condition for the removal of corresponding MBMS UE Context from the RNC. Then, after the procedure in which the UE 101 cancels a certain multicast service, the corresponding MBMS UE Context is still retained in the RNC. This might result in the fact that, in the subsequent distribution procedure of the MBMS Multicast Service data, even though the UE 101 has performed deactivation on a certain MBMS service and there is no other UE that has subscribed to this MBMS service in the cell where UE 101 is located, the RNC still allots it system resources and sends corresponding service data to the cell where the UE 101 is located. Such a result not only deviates from the object of cancellation of the MBMS service the UE 101 wishes to achieve through the deactivation procedure, but also is a waste of radio resources. Moreover, MBMS UE Context stored in each network element (UE, RNC, SGSN, GGSN) is inconsistent, while the RNC will keep the information which is virtually worthless, hence a waste of the RNC's storage space. Consequently, this might lead to hidden troubles and impair correct implementation of future products.